This invention relates to a four-roller workpiece bending machine, provided with a driven upper roller and a driven lower roller, and, more particularly, to a novel and improved four-roller workpiece bending machine having such a driven upper roller and a driven lower roller.
In some known machines of this type, the upper roller is inclinable and the lower roller is vertically displaceable. The two rollers are commonly driven by a locally fixed drive motor through a reduction gear and respective transmission shafts, with each transmission shaft being provided with two universal or cardan joints and a length compensating device, so that the lower roller may be displaced vertically and the upper roller may be pivoted. The drive motor may be an hydraulic motor or may be an electric motor. Also, two hydraulic or electric motors can be provided and be so connected that neither of the two rollers slides relative to the workpiece even when the workpiece has already been bent strongly and, in addition, is still relatively thick.
This kind of drive mechanism is difficult to manufacture and, moreover, requires a considerable amount of space, which is not always available in modern workshops.
There is also known an apparatus for the bending of metal sheets using two axially parallel driven lower rollers which are journalled in a horizontally displaceable carriage, and each of which, at one end, has a respective gear secured thereto and meshing with an intermediate gear journalled in the carriage. A non-driven upper roller is journalled externally of the carriage above the lower rollers. Two hydraulic motors are arranged on the carriage for driving the lower rollers, and are coaxial with the respective rollers. These hydraulic motors are connected to the associated lower rollers at respective opposite ends thereof. Thereby, it is attained that each lower roller is driven, at one end, directly by the hydraulic motor and, at its other end, through the meshing gears.
Although, with this apparatus, the power required to drive the lower rollers is reduced, the hydraulic motors must, however, and just as before, be so large that only expensive special productions can be used. Moreover, there still remains the considerable space requirement because of the large size of the hydraulic motors.
Another known sheet bending machine has an upper roller pivotable upwardly, about one end, for drawing off of the finished sheet metal cylinder, and at least two lower rollers which are angularly displaced relative to each other and which are displaceable relative to the upper roller. At least one of these rollers is driven. With a driven upper roller, a drive unit, consisting of an hydraulic motor with a reduction gear connected downstream thereof, is secured to the pivotable bearing block of this roller. The drive shaft of the reduction gear is coupled directly with the end spigot of the upper roller. With this arrangement, the drive unit is moved, together with the pivotable bearing block of the upper roller, and thus follows the pivoting out and in of the upper roller for the drawing off of the finished bent sheet metal cylinder.
Although a torque transmission shaft between the drive unit and the associated drive roller thus is no longer necessary, the reduction gear is still necessary in the same manner as before, which means an appreciable technical effort, forms a source of trouble, and increases the overall length of the sheet metal bending machine.